In recent years, 3D printers in which 3D design data is input to form three-dimensional objects (3D objects) in a printing-like manner have been commercialized. In the low price range (US$10,000 or less) mass market models, molten resin is deposited on a fabrication table from nozzles to form a thin layer and the thin layers are stacked to print a 3D object. The height per thin layer is about 0.2 mm. Mass market models are suitable for making toys etc.
On the other hand, to print 3D objects requiring high precision, middle price range medium grade models costing tens of thousands of U.S. dollars are necessary. Among medium grade models, there are ones which eject particles of resin to form layers for printing, Compared with mass market models which print by forming layers of molten resin, the surface finish becomes smoother. Further, among the medium grade models, there are ones which combine a number of types of materials to fabricate a 3D object. It is possible to form 3D objects with colors or 3D objects with transparent outside parts enabling the inside structure to be seen. Such medium grade models are suitable for fabricating prototypes meant for verifying the functions of the parts and for fabricating presentation use models.
Furthermore, high price range high grade models costing hundreds of thousands of U.S. dollars to a million U.S. dollars are designed for the manufacturing industry and enable fabrication of objects close to the final products. Therefore, high grade models are suitable for use in final checks of products, marketing, market surveys, etc. Further, among the 3D printers classed as high grade models, there are ones able to produce sand molds used for mass production of castings.
A 3D printer for producing sand molds is provided with a recoater able to store sand inside it and deposit sand from the tip in lines and an ink jet head. coating a binder on the sand thinly and uniformly deposited by the recoater on the printing table. In a 3D printer for producing sand molds, a layer of sand is thinly and uniformly deposited on a printing table, a binder is discharged and coated to solidify it, and these are stacked to form an object, then the object is calcined. A system for producing 3D objects from powder is disclosed in PLT 1.